Apparatus of the type mentioned above are known both in the sector of automatic beverage dispensing machines and in the sector of automatic machines used professionally in bars.
The various types of beverages which may be dispensed, as is known, comprise mainly cappuccino where an amount of—usually hot—foamed or frothed milk is added to the coffee, but also coffee with the addition of a small amount of hot or cold milk which is not frothed.
In the machines of the type mentioned above there therefore exists the need to have access to milk at various temperatures, ranging from cold to hot, and with a varying type of consistency, i.e. in ordinary liquid form or else foamed or frothed.
As regards the milk to be used in these types of machines and apparatus, as an alternative to fresh milk or long-life milk, the use of diluted concentrated milk has become more established recently, in particular in connection with machines which are intended to operate automatically, for obvious reasons associated with the difficulty or complexity of replenishing and storing the milk.
An example of use of fluid concentrated milk in order to obtain liquid milk by means of dilution with water is described in US-A-2005/0118319.
An example of a coffee machine with a frothing device which uses fluid concentrated milk which is liquefied by means of dilution with water is described in EP-A-1 747 743.
In accordance with that described and illustrated in the document mentioned above, the concentrated milk is liquefied using hot water which is drawn from a water heater of the coffee machine or by means of cold water drawn from a conventional source outside the machine.
Heating of the liquid milk, in accordance with the contents of the prior document cited, is therefore performed during dilution of the concentrate, while frothing thereof, using pressurised air and steam, is performed in the frothing device to which the liquid milk is supplied by means of the suction effect caused by the steam combined with the air.
The apparatus described by EP-A-1 747 743 therefore envisages two heating locations: the first one, during mixing and dilution of the concentrate when it is required to prepare non-frothed hot milk, and the second one in the frothing device when it is required to supply frothed milk, for example, for preparation of a cappuccino, it not being possible in this second location to obtain solely hot milk owing to the combined effect of the steam with the pressurised air.
It is clear that the provision of two different locations for heating the milk in order to be able to provide the apparatus with all the necessary flexibility as regards the temperature and consistency conditions required for the milk constitutes a drawback because it requires a greater corresponding functional complexity of the machine; this, owing to the particular nature of these machines which must operate mainly without the presence of dedicated personnel, has a negative effect on their reliability over time.